Hidden away, the siblings succumb to their forbidden desires, guilt-ridden yet unable to resist. The brother, his cock straining against his pants, begins to stroke himself, his eyes never leaving his sister's form. She watches, her breath hitching, her own body responding to the sight of him. She whispers, "You shouldn't," but her words hold no conviction. Her hand reaches out, tentatively at first, then with growing confidence, she grips his cock, her fingers wrapping around his width. He groans, his head falling back, as she begins to stroke him, her touch sending waves of pleasure coursing through his body.